Human three-dimensional visual perception, termed stereo vision, is related to the model human observer having two eyes that are located at two slightly different positions and that form two different viewing perspectives. These two different perspectives are interpreted by the brain and, for most people, effectively “fused” to form a single perspective image. This process, often referred to as binocular fusion, operates upon the disparity between the separate images that are simultaneously formed on the two retinas. Of particular interest for binocular fusion is the relative horizontal displacement of objects in the two images. In binocular fusion, a relative depth between objects is derived, resulting in the perception of a single, broad view with depth.
Stereoscopic display systems, in existence for a number of years, are based on the observation that it is possible to simulate three-dimensional (3-D) images by presenting a pair of two-dimensional (2-D) images separately to each eye, each image offering a different perspective of some captured or simulated scene content. There are a number of examples of 3-D or stereoscopic displays, using various techniques for distinguishing between the image intended for the left eye and the image intended for the right eye. With any type of stereoscopic display system, some type of separation mechanism is needed in order to distinguish the left (L) and right (R) images that appear on a common display, but are respectively intended for the appropriate left and right eyes of the viewers. Left- and right-eye images can be displayed at separate times, can be of different polarizations relatively orthogonal to each other, or can be of different wavelengths. Conventional two-projector systems can use any of these separation schemes or, alternatively a single-projector digital system using various techniques can also use any of these methods.
Time-sequencing systems use a “page flipping” technique and timing for left- and right-eye image separation. Page-flipping alternately displays left- and right-eye images to provide stereo images to one or more viewers wearing shutter glasses that have left- and right-lens opacity synchronized in some manner to the display refresh rates. One example of this type of display system adapted for presenting stereoscopic images to multiple viewers is disclosed in U.S. Pat. No. 6,535,241 (McDowall et al.).
Stereoscopic systems using polarization differences provide the left- and right-eye images using light at respectively orthogonal polarizations. Viewers are provided with polarized glasses to separate these left- and right-eye images. One example of this type of display system using linearly polarized light is shown in U.S. Pat. No. 7,204,592 (O'Donnell et al.). A stereoscopic display apparatus using left- and right-circular polarization is described in U.S. Pat. No. 7,180,554 (Divelbiss et al.).
Stereoscopic systems can separate left- and right-eye images by wavelength and provide viewers with filter glasses that are suitably designed to distinguish the appropriate image for each eye. One example of this type of spectral separation display system is shown in U.S. Pat. No. 7,001,021 (Jorke). 3-D display systems commonly require special eyeglasses to isolate the stereo information presented on the screen and direct that information to the intended eye, left or right. Such eyeglasses may be passive or active, the latter electronically synchronized to the display so as to allow each eye in turn to view only that information intended for that eye, while taking advantage of the limited response time of the human visual system to induce a stereoscopic effect. One example of active electro-optic eyeglasses is disclosed in U.S. Pat. No. 4,967,268 (Lipton et. al.).
To make a display capable of 2-D or 3-D operation, prior art systems require removal of the eyeglasses and manual switching of the display system into a 2-D mode of operation. Some prior art systems, such as U.S. Pat. No. 5,463,428 (Lipton et al.) have addressed shutting off active eyeglasses when they are not in use, however, no communications are made to the display, nor is it then switched to a 2-D mode. U.S. Pat. No. 7,221,332 (Miller et al.) describes a 3-D display switchable to 2-D but does not indicate how to automate the switchover. U.S. patent application Ser. No. 12/021,519 describes a switchable 2-D/3-D display system based on eyeglasses using spectral separation techniques, but again does not address automatic switching between modes.